A silicon ingot produced by the CZ method and the like has a cylindrical body portion and cone-shaped end portions (a top portion and a tail portion). In processing of the silicon ingot, these cone-shaped end portions are cut away to separate the cylindrical body portion, and the body portion is cut into a plurality of blocks as needed. The blocks are thereafter subjected to processing for obtaining wafers.
An inner diameter slicer and an outer diameter slicer or the like have been frequently used for the case of the cutting processing of the cone-shaped end portions and the cutting processing of the body portion into a plurality of blocks. As the diameter of the wafer becomes larger in recent years, a band saw also has become to be frequently used.
Here, FIG. 6 shows an outline of a method for cutting into a block in the case of using a band saw for an ingot cutting apparatus.
As shown in FIG. 6, a cutting table 105 for supporting the ingot at the time of cutting is arranged in the ingot cutting apparatus 101. Moreover, in the ingot cutting apparatus 101, an endless-belt blade (a band saw) 102 is provided in a tensioned state between pulleys 103 and 103′, and the blade includes a blade-abrasive-grain portion having abrasive grains of diamond adhered to an end portion of a thin blade base.
The ingot 104 is horizontally placed on the cutting table 105 before cutting. A position where the ingot 104 is placed is adjusted so that a cutting position of the ingot 104 corresponds to that of the blade 102.
The blade 102 is driven to rotate by rotating the pulleys 103 and 103′, and the ingot 104 is cut by relatively feeding the blade 102 from above to below against the ingot 104. In this point, a coolant is supplied to the blade 102 for the purpose of, for example, removing processing heat at a cutting area and cutting chips. The coolant is supplied mainly through a nozzle 108 for spraying the coolant.
As the cutting is repeated, cutting capacity becomes low because some abrasive grains are buried due to accumulation of cutting powder on the blade-abrasive-grain portion and the like. Therefore, the blade is periodically subjected to dressing process.
A conventional ingot cutting apparatus and method, however, has a problem that the coolant is not sufficiently supplied to the blade-abrasive-grain portion of the blade 102, which operates upon the cutting most, and consequently the processing heat and the cutting chips cannot be sufficiently removed.
With regard to this problem, there is disclosed a band saw cutting apparatus and a cutting method that allegedly enables the coolant to be sufficiently supplied by spraying the coolant through a spray nozzle from the side of a cutting direction of the blade to an edge portion of the blade (See Patent Literature 1).